Railway traffic controlling apparatus



1940' F. H. NICHOLSON ET AL 2,213,120

RAILWAY TRAFFIC CONTROLLING APPARATUS ori inal Filed May 28, 1958 aSheets-Sheet 1 INVENTORS fizllzlili v'clwlswzzznd L l3 flllz'son THEIRATTORNEY 1940 F. H. NICHOLSON El AL 2,218,120

' RAILWAY TRAFFIC cou'monmm APPARATUS Original Filed May 28, 1938 sSheets-Sheet 2- 5 5 I U V L- 180C0de 180C0de 75Code 15 Code Yhzini l f II X r- X iii 2 HM Su 50 5w 5x moi/ET INVENTORS iflzzzzfiliNz'c/zolwn andLe Bflllison.

' THEIR ATTORNEY Oct. 1940' F. H. NICHOLSON ET AL 2,218,120

RAILWAY TRAFFIC CONTROLLING APPARATUS I Original Filed May 28, 1938 3Sheets-Sheet 3 T' J .93 L

m0 H (B BY le flflllzson. .96 Z5 g l THEIR ATTORNEY T0176 JB- 153%INVENTORS Patented Oct. 15, 1940" RAILWAY TRAFFIC, CONTROLLING APPARATUSFrank H. Nicholson, Wilkinsburg, and Leslie R.

2 Allison, Forest Hills, Pa., assignors to The Union Switch & SignalCompany, Swissvale, Pa., a corporation of Pennsylvania Originalapplication May 28, 1.938,- Serial No. 210,744. Divided and thisapplication July 22, 1939, Serial No.,286,030 V 8 Claims. (Cl. 246-34)Our invention relates to railway traffic controlling apparatus and ithas special reference to the organization of such apparatus intosignalling systems of the class wherein a'code-following relay at eachwayside location and/or on v atrain receives coded operating energy fromthe trackway and in accordance with the character of that energy effectsvarious control functions through the medium of associated decodingequipment.

This application is a division of our earlier ap-.

plication bearing Serial No. 210,744 which was filed May 28, 1938, forRailway traffic controlling apparatus and. assigned to The Union Switch& Signal Company.

As in that earlier'case, the broad object of the present invention is tolower the cost, simplify the construction and improve the operatingcharacteristics of decoding equipment of the referred to type. V

A more specific object is to assure that this equipment will not falselyrespond when rectifier or other foreign ripples are present in thedecoding transformer supply circuit.

Another object is to'safeguard the decoding equipment against falseresponse in the event that the front and back contact points of theassociated code following relay become accidentally interconnected.

An additional object is to permit the code following relay safely to beadjusted for closer spacings between themovable member and the front andback points of each of its contact sets.

A further object is to assure that the wayside decoding equipment willrespond to each initial shunting of the associated track circuit with aquickness which is adequate for all possible train running conditions.

A still further object is to detect codes and distinguish betweendifferent pulse rates thereof without employing the usual resonant orfrequency tuned circuits.

An additional object is to provide the above features of operationthrough the use of a restricted. number of contacts on the codefollowing relay.

A still additional object is to accomplish the above without dispensingwith any of the desirable features of continuously coded track cir- Jcuit control."

In practicing our invention we attain the above and other objects andadvantages by associating the various decoding equipme'ntparts with thecode following relay in new and improved manners. Involved in theseassociations are a number of cooperating features of which introductorymention will here be made of but two: (1) Rectifying the secondaryvoltage of the decoding transformer over a contact of the code followingrelay and using this rectified output to energize a code detectingrelay, and (2) Se rially including inthe primary supply circuit of thedecoding transformer the windings of relays which repeat the'front andback contact closures of the code. following re1ay., n

We shall describe several forms of railway traffic controlling apparatusembodying our invention and shall then point out the novel featuresthereof in claims. These illustrative "embodiments are disclosed in theaccompanying drawings, in which:' j I Fig. l is a diagrammatcrepresentation of traflic governing apparatus embodying the feature ofour invention first named above;"

Figs. 2, 3 and 4 are diagrammatic showings of one applicationoflthe'principles of ourinven.- tion' to a combined wayside and cabsignalling system of the three indication'typ'e;

Fig. 5 is a similar representation of an application wher'ein'the numberof wayside signal indicationsis extended to four; and v Fig. 6 is adiagrarmnatic view of a still further application of the improvements ofour invention to a railway signalling system. I

In the several views of the drawings, like reference charactersdesignate corresponding parts. Referring first to Fig, ,1, character.TR. designates a track relay of the code following type, DT' a decodingtransformer" which receives primary current under the controlof' a polechanging contact 4 of the track relay, H acode detecting relay of thedirectfcurrent delayed releasetype which is energized from a;secondarywinding Ill of the decoding transformer and'DI80 a code distinguishingrelay which is energized from a second secondary winding 9 of thetransformer addition, therefore, to being a track relay as shown, itmay, for example, also be a train car- .ried master relay adaptedtocontrol a cab signal, or a code following relay which receivesoperating energy over line wires. In [the illustrative applicationrepresented in Fig. 1, this relay TR' is directly connected to the rails{l and 2 of a section of railway track E-F which isseparted fromadjoining sections by the customary insulated joints 3 and along whichit will be assumed that traffic moves in the single direction indicatedby the arrow.

Installed at the opposite or exit end of the section is a source oftrackway energy, shown in the form of a direct current battery 5, whichis connected to the rails I and 2 over a contact 6 of a relay CR and byway of a circuit which ineludes the usual current limiting impedance I.Each time that contact 6 is in its uppermost position, the rail supplycircuit is completed and the voltage of battery 5 thenis'impressedbetween the rails and by them transmitted to the winding of relay TR at.the opposite or entrance end of the section. Each time, however, thatcontact 6 occupies its open position, the rail supply circuit isinterrupted and the winding of the track relay TR then. is deenergized.

Device CR typifies apparatus for coding the trackway energy at one oranother of aplurality of distinctive rates in accordance withpreselected conditions. In the system of Fig. 1, it will be assumed thatunder certain conditions of advance tralfic this deviceperiodicallyactuates its contact 6 at one rate to provide what will be termed a lowspeed? code and that under other conditions it increases the rate ofperiodic opening and closing of the rail supply circuit to provide whatwill be referred to as a high speed code. In receiving this codedenergy, relay TR picks up its contacts upon the occasion and for theduration of each pulse thereof and releases its contacts each time thatthe relay winding is deenergized; thereby repeating the operation of thecoding relay CR.

Aside from having two separate secondary windings, the decodingtransformer which is shown at DT in Fig. 1 is of the conventional typeand under the control of contact 4 of the code following relay TR itssingleprimary winding receives energizing current from any suitabledirect current source, designated by the terminals plus and minus.In-territory in which the energy for operating the signalling system issupplied from analternating current transmission line (not shown)which-runs along the rightofway in the customary manner, these terminalsare usually identified with the output circuit of a rectifier of thefull wave type shown at Z. Typically, such a rectifier consists of fourbranch paths or units,8 interconnected in the manner shown, andordinarily its input terminals receive 100 cycle or other signalfrequency energy from the mentioned power supply line through a circuitwhich includes a transformer 2I and power source terminals B and C.

Each time that the pole changing contact 4 of relay TR is picked up,direct current flows downwardly through one portion of the transformerprimary and. by way of a circuit shown as extending from the positiveterminal of rectifier Z, through front contact 4, conductor I8, theupper half of the transformer winding, and mid tap I9 back to thenegative terminal of the supply rectifier. Likewise, each time thatcontact 4 is released, current flows in the opposite direction orupwardly through another portion of the winding and by way of a circuitshown as extending from the positive supply terminal through backcontact 4 of device TR, conductor 22, the

" lower half of the transformer winding, and mid DI 80 responds as aresult of its Winding receiving actuating energy from the secondarywinding 9 of transformer DT through the tuned circuit J I80 which isarranged to be resonant to the high speed frequency only. If, however,the referred to frequency is of the low speed" rate, this tuned circuitfails to transmit sufficient current to operate relay DI80 and thecontacts of that relay then are released.

As a result of incorporating the improvements of our invention, theenergizing circuit for the code detecting relay H functions to supplyuni directional operating current to that relay whenever the track relayTB is following either the high speed.or the low speed code. In eitherevent, the alternating voltage whichis generated in the secondaryWinding II) of the decoding transformer DT is rectified over a secondcontact II of the code following relay TR and in-this rectifiedcondition it is impressed upon the direct current winding of the relayH.

The particular circuit shown, therefore, causes unidirectional currentto be supplied to relay H. To this end the transformer winding I0 isprovided with a mid tap connection I2 which is joined, through aconductor I3, with one side of the H relay winding and the other side ofthe relay winding is connected to the, heel of contact II by means of aconductor I4. Finally, the end terminals of the secondary winding IIIare joined to the front and back points, respectively, of contact I I bymeans of conductors I6 and II.

In operation, each time that contact I I is in its picked up position,the winding of relay H is connected with the lower half of the secondarywinding III of the decoding transformer DT through a circuit whichextends from the mid tap I2 of that winding, through conductor I3, thewinding of relay H, conductor I4, front contact II, and conductor I6back to the lower terminal of winding II). In consequence, what will bereferred to as the positive half cycles of the induced transformervoltage become effective for circulating current through the winding ofrelay H.

Likewise, each time that the track relay contact II is in its releasedposition, the winding of relay H is connected with the upper half. ofthe transformer secondary I0 through a circuit which may be traced fromthe mid tap I2, through conductor I3, the winding of relay H, conductorI4, back contact II, and conductor I! back to the upper terminal ofwinding I0. In consequence, what will be termed as the negative halfcycles of induced transformer voltage also become effective to providecurrent flow through the winding of the relay. I

To clarify the foregoing explanation, the direction of current fiowduring the positive half cycles of induced transformer voltage isdesig-, nated in Fig. l by the small full line arrows while thedirection of current flow during the negative half cycles of thisvoltage is similarlyde signated by the small broken line arrows. Fromthat explanation it will be apparent that the winding of code detectingrelay H receivesrecurring pulses of unidirectional energizing currentduring the continuance of each code following operation which iseffected by relay TR. I

The constants of the H relay energizing circuit are so chosen that thesepulses are effective to pick up the relay contacts. In order that thispicked up condition may be retained continu- 5 ously as long as relay TRcontinues to follow a trackway code, relay H is further designed tohavesuificient release retardation to span the open circuit intervalduring which the contacts of relay TR move from one position to theother in response to the current pulses of the coded operating energy.For this purpose, any one of a number of familiar expedients may, ofcourse, be

used. As shown in Fig. 1, the release delay is provided by means of .asnubbing resistor 23 which is 5 bridged across the terminals of thewinding of relay H in a well-known manner.

In operation of the just-described decoding equipment of Fig. 1, whenthe contacts of the code following relay TR occupy one positioncontinuously (as, for example, when the relay fails to receive codedenergy from the track section E-F) decoding transformer DT passes noenergy and the contacts of both of the relays H and Dl8fl then occupythe deenergized or released posi- 26 tion. Each time, however, thatrelay TR receives and responds to a trackway code, contacts land 1thereof simultaneously pole change the primary and secondary circuits ofthe decoding transformer and in consequence the contactsof relay H arethen picked up, as are also those of relay DiStl when the responded tocode is of the high speed frequency. In other words, as long as relay TRfails to receive coded energy, the contacts of both of the relays H andD189 occupy their released positions; when relay TR'responds to the slowspeed code, the contacts of code detecting relay H only are picked up;and when relay TR responds to trackway energy of the high speed code,the contacts of the code distinguishing relay Dl80 are also picked up.

Any desired use of the just-described response characteristics of relaysH and D180 may, of course, be made. As shown in Fig. 1, the representedcontacts 24 and 25 of these devices are arranged to control theenergizing circuits for the lamps of a wayside signal Se. This signal isof a well-known color light type and comprises three lamps G, Y and Rwhich, when lighted, respectively project into the range of vision ofthe 60 engineman of an approaching train beams of light having thecolors of green, yellow and'red.

Assuming that the apparatus of Fig. 1 is combined into a system ofautomatic block signalling in the manner partially represented, theoperation will be as follows: As long as the rails I and '2 transmitenergy of the high speed code to the track relay TR, lamp G of signal Sewill be lighted to display the clear indication as a result of relays Hand Dl80 both being energized and completing for the lamp an energizingcircuit which may be traced from the positive terminal of a suitablesupply source through front contact 24 of relay H, front contact 25 ofrelay Dl80, conductor 26 and the lamp G back to the negative 65,terminal of the supply source.

When the track relay TR receives energy of the slow speed code, thecontacts of relay H only will be picked up and the signal will thendisplay the approach indication as a result 'of lamp Y receivinglighting current over a circuit which extends from the positive supplyterminal through front contact 24 of relay H, back contact 25 of relayDl80, conductor 2'! and the lamp Y back to the negative supply terminal.Finally, in the event that the relay TR fails to receive coded energy,as when the track section E-F is occupied, the contacts of both relays Hand Dl will be released and the signal will then display the stopindication as a result of lamp R receiving lighting current over acircuit 5 which extends from the positive supply terminal through backcontact 24 of relay H, conductor 28 and the lamp R back to the negativesupply terminal. 1

Among the advantages afforded'by our im- 10 proved arrangement of Fig.1, mention may be made of the simplification of code detecting apparatusand also of the superior operating characteristics. Regarding theformer, the single relay H performs all of the code detecting func- 15tions for which a pair of repeater relays (for the front and backcontacts of the code following device) formerly have been required andthus this expedient reduces both the cost and complexity of decodingequipment of. the character 20 under consideration.

Regarding the improvement in operating characteristics, the novelfeature described above effectively guards against the display of afalse approach wayside indication should rectifier ripples be introducedinto the decoding transformer supply circuit or should the front andback contact points of the code following relay TR accidentally becomeinterconnected, as by fusing due to lighting. In the latter event, if 30the interconnection involves the points of contact H, the resultingshort circuiting of the transformer secondary ID will permanentlydeenergize relay H and thereby efi'ect completion of the circuit for thestop lamp R of the associated 35 signal S. Likewise, if the faultycondition referred to takes place at pole changing contact 4,transformer DT will transfer no energyat, all and relay 1-1 will againbe deenergized continuously. 4o

Concerning the introduction of rectifier or other foreign ripples intothe decoding transformer supply circuit, this may happen as a result,for'example, of failure of one of the-branch units 8 of the supplyrectifier Z. If the energy 45 were supplied to relay H by means of theconventional static circuits (comparable to J I80 but untuned) theseripples might, due to alternation of the primary current of transformerDT, effect actuation of that relay under conditions 50 of contactstalling by relay TR.

With the circuits of Fig. 1,- however, such false response by thedecoding equipment is effectively guarded against, for with contact llstalled in either position, the winding of relay H is con- 55 tinuouslyconnected to the decoding transformer secondary l0. Being of the directcurrent design, this relay H is incapable of picking up on any resultingalternating current which it may receive and in this manner falseresponse to foreign 50 current ripples in the transformersupply circuitis effectively prevented.

An attendant advantage of the arrangement of Fig. 1 is that the corefollowing relay TR may now safely be adjusted for closer. spacings be-55 tween the movable member and the front and back'points of each of itssets of contacts. In previous decoding arrangements, safety requirementsmade it imperative that relatively wide contact spacings be used inorder to avoid any 70' possibility of false operation. However, by meansof our improved apparatus, the contact spacings may safely be reduced toa value which is limited only by the normal operatingcharacteristics ofthe code following device. By thus lowering the 5 range of movablemember travel, such a reduction has the effect of raising the efficiencyof the relay TR and hence is most desirable from an operating point ofview.

Referring now to Figs. 2 and 3, these show another application of theimprovements of our invention to an automatic block signalling system ofthe three indication type. Fig. 2 represents: a stretch of protectedtrack which includes four section dividing locations U, V, W and X; thedistribution of the coded train control energy which is present in thefour track sections immediately behind a train A; and the aspects of theassociated wayside signals S.

From Fig. 2 itwill be seen that three codes designated as I5, 15 and Iare employed. These are respectively produced by correspondinglydesignated contacts of a code transmitter GT5 forming a part of theapparatus of Fig. 3 which is installed at each of the section dividinglocations. In the particular system represented, the trackway energy isderived from an alternating current source, designated by the terminalsB and C, and is transmitted to the trackway through the medium of theusual track transformer TI. Use also is made of alternating currenttrack relays TR of the code following type and of three aspect colorlight wayside signals S of the character shown in Fig. 1.

The apparatus of Fig. 3 further employs front and back contact repeaterrelays FF and BP which cooperate in a novel manner with the codefollowing track relay TR and the decoding transformer DT5. The windingsof these repeater relays are included in the conductors l8 and 22 of thedecoding transformer supply circuit in a manner which causes the relaysalternately to be energized over contact 4 of the track relay.

Each time that this contact is picked up, the resulting current whichflows through the upper half of the transformer primary (again from asource designated by the terminals plus and minus) passes through thewinding of relay FP; likewise, each time that the contact 4 is in itsreleased position the resulting flow of current through the lower halfof the decoding transformer primary similarly energizes the secondrepeater relay BP over a path which includes a front contact 36 ofdevice FP. Through an employment of means not represented, each of theserelays is provided with a retardation sufficient to maintain thecontacts thereof continuously picked up when the track relay responds toa code frequency of 15 cycles per minute or higher.

The code detecting relay shown at H15 in Fig. 3 receives energizingcurrent from the secondary winding of the decoding transformer DT5 overcircuits which include contact I l of the code following relay TR. Thatcontact controls the relay current in the same manner as has beenexplained in connection with Fig. 1. This H15 re;- lay, however, doesnot pick up on the lowest or l5 code and responds only when the codefrequency is of the medium. or 15 pulse per minute order or higher.

This selective characteristic is preferably obtained by designing thedecoding transformer DT5 to have special saturating characteristics as aresult of which the amount of energy transferred at the low or l5 codefrequency is insufficient to pick up the relay contacts. Conveniently,such characteristics may be provided by making the magnetic circuit ofthe transformer of comparatively small cross section and so 00-ordinating the primary and secondary windings therewith that the speedof operation of contact 4 of relay TR must at least approach the 15 coderate before the induced secondary voltage will be adequate to circulatecurrent of pick-up strength through the winding of relay H15. When thusarranged, relay H15 maintains its contacts in the released position aslong as the relay TR responds to a code as low as 15 cycles per minute.However, on a code frequency of 75 cycles per minute or higher, therelay picks up its contacts and holds them continuously at full stroke.

For the purpose of controlling the lamps of the wayside signal Su,relays BP and H15 are provided with contacts and 9| which control thelamp lighting circuits in the usual manner. Likei wise, for the purposeof selecting which of the three contacts 15, 15 and I88 of the deviceGT5 is included in the primary winding circuit for the track transformerTI connected to the rails of the rear track section, these two relays BPand H15 are further provided with contacts 92 and 93. Further includedin the rear section rail supply circuit is a contact 94 of the repeaterrelay FP, which contact functions to quicken changes in signal aspect ina manner later to be described. In operation of these signal control andcode selecting circuits, when the track relay TR fails to receive codedenergy, as in the event that a train occupies the associated tracksection (as shown ahead of location X in Fig. 2), the resultingdeenergization of all three of the relays BP, 13? and H15 causes theircontacts to be released. In consequence, the wayside signal Su showsstop by virtue of lamp R thereof being lighted over a circuit whichextends from the positive supply terminal through back contact 90 ofrelay BP, conductor 28, and the lamp R back to the negative supplyterminal. At the same time, the rails of the track section to the rearreceive energy of the l5 code over a circuit which extends from thesupply terminal B through coding contact I 5 of device GT5, conductor96, back contact 92 of relay BP, conductor 5| and the primary winding oftransformer 'IT back to the supply terminal C.

At the entrance of the first vacant block behind the train, oratlocation W in Fig. 2, the response by the track relay TR to this 15 codecauses the contacts of relays FF and BP only to be picked up. Under thiscondition, the controlled wayside signal Sw shows the indication of"approach by virtue of lamp Y thereof receiving lighting current over acircuit which extends from the posi tive supply terminal through frontcontact 90 of relay BP, back contact 91 of relay H15, conductor 21 andthe lamp Y back to the negative supply terminal. At the same time, therails of the track section to the rear of the location receive energy ofthe 15 code over a circuit which extends from the supply terminal Bthrough coding contact 15 of device GT5, conductor 98, back contact 93of relay H15, conductor 99, front contact 94 of relay FP, conductor I00,front contact 92 of relay BP, conductor 5| and the primary of tracktransformer T1 back to supply terminal C.

At the entrance of the second vacant section behind the train, or atlocation V in Fig. 2, the response by the track relay TR to this 15 codecauses the contacts of all three of the relays FP, BP and H15 to bepicked up. Under this condition, the wayside signal Sv displays theindication of clear by virtue of lamp G thereof receiving lightingcurrent over a circuit which extends from the positive supply terminalthrough front contact 90 of relay BP, front contact 9| of relay H15,conductor 26 and the lamp G back to the Lil ill)

pulses of primary current,'decoding relays which negative supplyterminal. At the same time, the rails of the rear track section receiveenergy of the I80 code over a circuit which may be traced from thesupply terminal B through coding contact I88 of device GT5, conductorI03, front contact 93 of relay H15, conductor 99, front contact 94 ofrelay FP, conductor I00, front contact 92 of relay BP, conductor and theprimary of transformer TT back to the supply terminal C.

At the entrance of the third vacant block behind the train, or atlocation U in Fig. 2, the response by the track relay TR to the ISO codeagain causes all three of the relays FP, BP and H to be picked up andproduce the clear indication on the part of the controlled signal Su andan inclusion of the coding contact I 80 in the rail supply circuit forthe rear section. These conditions, moreover, are also duplicated ateach of the locations further to the rear :vhich are associated withunoccupied track secions.

Regarding the action of the contact 94 of relay FP in the rail supplycircuit, it has been indi-- cated that this contact functions to quickenthe change of signal aspect. This quickening occurs as a result of thefact that upon a stalling of the track relay TR in response to an entryof a train into the associated track section, relay FP must release itscontacts before the winding of relay BP can be deenergized by a breakingof its supply circuit at contact 35. Accordingly relay BP does notrelease its contacts until after its full period of drop out delay hasexpired following theopening of the contacts of relay FF, and thecontact 92 thereof thus does not transfer the coding device connectionfrom the 15.

contact to the i5 contact until some time following the release of relayFP.

It will thus be seen that by including contact 94 of the latter relay'inthe rail supply circuit in the manner shown, the supply of all energy tothe rails of the rear track section is temporarily cut off by therelease of the contacts of relay FF and resumed at the lowest or i5 codeupon the subsequent release of the contacts of relay BP. In a system ofthe character shown in Fig. 3, this action is a desirable one in that itsubstantially accelerates response of the cooperating apparatus at theentrance end of the rear section.

The selection of codes just described in connection with Figs. 2 and 3affords special advantages when the trains which pass through theprotected stretch of track are'equipped with cab signalling apparatus ofthe conventional type which does not respond to code frequencies as lowas the 15 pulse per minute value. As has been seen, energy of that lowfrequency code is sup plied to the rails of the track sectionimmediately behind the one occupied by an advance train. One verypractical benefit is that a one block overlap for the control of astopcab. signal is obtained without enforcinga corresponding stop indicationat the wayside signal.

Typically, the referred to train carried cab signalling apparatus may beof the construction shown and described in United States Patent No.1,773,472 granted to Paul N, Bossart on August 19, 1930, for Railwaytraffic controlling apparatus. Such apparatus makes use of devices forinductively receiving energy from the track rails, an amplifier whichstrengthens the received energy, a code following master relay which isenergized from the amplifier output, a decoding transformer which issupplied under the control of the m'aster'relay with code following areconnected with the decoding transformer through frequencyselective'circuits, anda cab signal having a plurality of indicatingunits which are selectively energized under the control of the decodingrelays.

In the event that a train ipro lded with equipment of the character justdescribed passes over the "protected stretch of the track which isrepresented in Figs. 2 and 3, a'three unit cab signal thereof of thetype shown at CS in Fig. 2 will respond in the manner there representedas the train progresses through the successive sections behind theadvance train A. Of this sig- -nal, the top unit is assumed to designatefull authorizedspeed', the center lamp approach speed, and the lowerlamp the most restrictive or stop indication.

When the signal carrying train' is receiving the equipment fails torespond and the lower lamp of the signal then lights to display theindication in Fig. 3 are there represented as being applied to a cabsignalling system which is arranged to cooperate with the trackwayapparatus of Figs. 2 and 3 in a manner which causes a cab signal CS6 torepeat on board the train the indications which the wayside'signals S ofFigs. 2 and 3 display along the wayside. In this modification, it

will be understood that the cab signalling apparatus is so designed thatit responds to I5 code as well as to I5 code. v

This signal CS6 takes the form of three lamps which are selectivelysupplied with energizing current over circuits which are controlled bythe contacts 90 and 9! of relays 'BP and H15. These relays together witha companion device FP are duplicates of those shown and described inconnection with the apparatus of Fig. 3. They,'to'- gether with adecoding transformer D'I5, are controlled by a train carried 'master or'code following relay MR which corresponds to the track relay TR of thecooperating wayside apparatus of Fig. 3.

This masterrelay is of the direct current polar- I06 and III! which arerespectively included in the circuits of the repeater relays FF and BPand of the code distinguishing relay H15. The relay MR receivesoperating current from an amplifier of any suitable well-knowncharacter, which, in turn, is controlled by the output voltage of a pair'of windings I08 of the usual receiver I08--I09 which is mounted aheadof the advance truck of the equipment carrying vehicle just above andspanning the two rails I and 2. When alternating ,current of thecharacter supplied from source B-C' flows in the rails, voltages areinduced in and additively combined by these windings.

Like relay TR in the system of Fig. 3, the train carried master relay MRshown in Fig. 4 follows the coding of the energy transmitted theretofrom the track rails I and! through the receiver Windings ID8,'theamplifier, and. the relay transformer nal.

RT. Both of its contacts I06 andv I01 shift from one position to theother when the polarity of the relay energization changes and when therelay is de-energized these contacts stay in the position to which theywere biased by the last energization of the relay. Thus, at thebeginning of each pulse of trackway energy (when buildup of current inthe primary of transformer RT induces in the transformer secondary asurge of given polarity voltage), the contacts are moved to theright-hand position (shown heavy) and at the end .of each energy pulse(when decrease of current in the primary of transformer RT induces inthe transformer secondary a surge of opposite polarity voltage) they arereturned to the left-hand position (shown dotted) where they remainuntil another pulse of energy appears in the trackway.

The operation of the cab signalling apparatus of Fig. 4 is similar tothat of the wayside signalling equipment previously explained inconnection with Fig. 3. When the receiver I08 picks up no energy at allor uncoded steady energy, the contacts of master relay MR are at restand relays BP and H15 then are both deenergized. Under this conditionthe cab signal CS6 displays the indication of stop by virtue of thebottom unit thereof receiving lighting current over a circuit whichextends from the positive supply terminal through back contact 90 ofrelay BP, conductor III, and the unit itself back to the negative supplyterminal.

When the received energy is of the 15 pulse per minute code, theresulting response thereto by the master relay MR causes the contacts ofrepeater relays FF and BP to be picked up and still allows those of H15to remain released. Under this condition, the cab signal CS6 displaysthe approach indication by virtue of the middle unit thereof receivinglighting current over a circuit which extends from the positive supplyterminal through front contact 90 of relay BP, back contact 9| of relayH15, conductor H2, and the unit itself back to the negative supplyterminal.

Finally, when the received energy has a code rate of '75 pulses perminute or higher, the contacts of all three of the relays FP, BP and H15are picked up and the cab signal CS then displays the clear indicationby virtue of the top unit thereof receiving energizing current over acircuit which extends from the positive supply terminal through frontcontact 90 of relay BP, front contact SI of relay H15, conductor I I3,and the unit itself back to the negative supply termi- It will be seen,moreover, that energy of the 180 code has the same effect as does thatof the 7 code just described in acting to produce the clear indicationof cab signal CS6.

With the exception of the fact that the contacts I06 and I01 of themaster relay MR are substituted for contacts 4 and II, respectively, ofthe track relay TR, the relay and the decoding transformer circuitsshown in Fig. 4 are duplicates of those previously explained inconnection with Fig. 3. Hence, the train carried relay MR controls thesecircuits in precisely the same manner as does the wayside track relayTR. The arrangement of Fig. 4 thus provides a three indication cabsignal system without the use of the usual resonant or frequency tuneddecoding circuits. In it, as has been seen, the approach indication isobtained with code (instead of 75 code as at present) and the 180 codehas no different effect on the apparatus than does the 75 code whichproduces the clear indication.

Likewise, the wayside apparatus of Fig. 3 also offers the same advantageof detecting codes and distinguishing between different pulse ratesthereof without employing frequency tuned circuits. As these involvecomparatively bulky and expensive apparatus the stated advantage is apractical one. Moreover, through the represented inclusion of contact 94of relay FP in the rail supply circuit for the rear track section, theequipment of Fig. 3 provides a shunting response having a quicknesswhich is adequate for all train running conditions.

Referring to Fig. 5, we have there shown a further application of theimprovements of our invention to a system of automatic block signallingwherein the number of wayside indications is extended to four. In thisapplication, there is installed at the entrance end of each blocksection the equipment which is shown at the single location U of thedrawing figure.

This equipment includes a code following track relay TR of thealternating current type already described, a decoding transformer DT1controlled by contact 4 of that relay in the same manner as in thesystem of Fig. 1, a pair of relays FF and BP arranged to repeat thefront and back positions of a second contact I04 of relay TR, a firstcode distinguishing relay H15 which is energized from secondary 89oftransformer DT1 and a second code distinguishing relay DI80 which isenergized through frequency selective circuits J I80 that are connecteddirectly across the end terminals of the decoding transformer primary.

The facilities for coding the trackway energy are the same. as thosedescribed in connection with the system of Fig. 3. They include a codetransmitter GT5 having three contacts I5, 15 and I80 which, under thecontrol of contacts 92 and 93 of relays BP and H15, are selectivelyconnected in the rail supply circuit to interrupt the supply of primarycurrent to transformer TT at the rate of 15, '15 or 180 times perminute. To quicken the shunting response of this apparatus use also ismade of a contact 94 of relay FP, again arranged as in Fig. 3.

Regarding the wayside signal Su, it consists of five lamps controlled bycontacts I21, I28 and I29 of relays BP, H15 and DI80 to give the fourdifferent indications which will be described presently.

In operation of the delays of Fig. 5, devices FF and BP respond in thesame manner as in the system of Fig. 3. That is, both respond to thepresence of coded energy in the associated track section. Consequently,trackway energy of any one of the three 15, 75 and 180 codes iseffective to pick up both of devices FF and BP. The relay controlcircuits shown differ from those of the earlier figures only in that aseparate contact I04 of the track relay TR is used to control therepeater devices.

The first code distinguishing relay H15 picks up only in response tocodes of the 75 pulse per minute rate or higher. It is of the samedirect current type as that used in the system of Fig. 3 andrectification of its energizing current is effected by a full waverectifier IIB. As in the case of the decoding transformer of the systemof Fig. 3, transformer DT1 is so designed that at code frequenciessubstantially below the 75 rate it fails to transmit suflicient energythrough its secondary winding 89 to pick up the contacts of relay H15.

To safeguard that relay against false response ill when rectifier orother foreign ripples are present 15 in the decoding transformer supplycircuit, a contact 31 of relay 3? is interposed between winding 89 ofthe decoding transformer and the winding of relay H15 suppliedtherefrom. If, now, relay TR is not following code, this contact opensthe circuit under consideration and thus provides the protection juststated. Obviously, the same result may be obtained by interposing thecontact 31-between relay H15 and rectifier I I6 (as in Fig. 6) insteadof between the rectifier and transformer winding 89 as shown.

The second code distinguishing relay DI80 picks up only in response tocodes of the 180 pulse per minute rate or higher. It, therefore, is thefull equivalent of relay DI80 of Fig. 1.

In operation of the complete signal location equipment of Fig. 5,whenever the track relay TR fails to receive coded energy, as in theevent that the track section ahead of location U is occupied, thecontacts of all three of the relays BP, H15 and DI80 are released. Underthis condition, the rails of the rear track section receive energy codedby contact I5 of device T5 and the wayside signal Su displays theindication of stop as a result of lamp R thereof receiving lightingcurrent over a circuit which extends from the positive supply terminalthrough back contact I21 of relay BP, conductor I3I and the lamp R backto the negative supply terminal.

When energy of the I5 code is received by relayTR, the contacts ofrelays FF and BP only are picked up. Under this condition the rails ofthe rear track section receive energy coded by contact of device GT5 andthe signal Su displays the indication of approach as a result of itslower lamp Y receiving lightin current over a circuit which extends fromthe positive supply terminal through front contact I21 of relay'BP, backcontact I28 of relay H15, conductor I32, and the lamp Y back to thenegative supply terminal.

When energy of the 15 code is responded to by relay TR, the contacts ofrelay H15 also are picked up. Under this condition the rear tracksection is supplied with energy coded by contact I80 of device 0T5 andthe wayside signal Su shows the approach medium indication as a resultof its upper lamp Y and its lower lamp G being simultaneously energizedover a circuit which extends from the positive supply terminal throughfront contact I21 of relay BP, front contact I28 of relay H15, backcontact I of relay DI 80, conductor I33 and both of the named lamps backto the negative supply terminal.

Finally, when energy of the I80 code is responded to by relay TR, thecontacts of all four of the relays FP, BP, H15 and DI80 are picked up.Under this condition the track section to the rear of location U isagain supplied with energy coded by contact I80 of device GT5 and thewayside signal Sn displays the clear indication as a result of its upperlamp G receiving lighting current over a circuit which extends from thepositive supply terminal through front contact I21, I28 and I29 inseries, conductor I34 and the lamp G back to the negative supplyterminal.

Regarding the advantages of the arrangement of Fig. 5, the representedinclusion of contact 31 of relay BP in the energizing circuit for relayH15 assures that the latter relay will not falsely respond whenrectifier or other foreign ripples are present in the supply circuit ofthe decoding transformer DT1. Moreover, the use of contact 94 of relayF]? in the rail supply circuit assures the same quick shunting responseas was dise cussed in connection with Fig. 3.

Referring to Fig. 6, we have there represented a modified form ofcircuits for obtaining the same wayside and cab signal operation as theFrank H. Nicholson on March 30, wearer Rail-.

way trafiic controlling apparatus. Also, the energizing circuit for thecode distinguishing relay H15 is modified touse, as does the apparatusof Fig. 5, a full wave rectifier II6 of thecopper oxide or otherequivalent type, which is connected with the single section secondarywinding 89 of the decoding transformer DTB.

The primary winding of this transformer is controlled by contact 4 ofrelay TR in the same manner as that explained in connection with therepresentation of Fig. 1. As in the case of device D T5 of Fig. 3, thedecoding transformer DT8 of Fig. 6 is designed to transmit to relay H15sufficient energy to cause it to pick up its con-' tacts only when thefrequency of the coded energy to which the track relay TR responds has avalue of 75 cycles per minute or higher.

Repeater relay BPI5, however, is arranged to pick up its contacts uponcode frequencies of 15 cycles per minute or higher. Moreover, it isprovided with a contact 31 which is included in the supply circuit ofrelay H15 and arranged, as in the system of Fig. 5, to eliminate thepossibility of falsely energizing that relay when ripples of rectifieror other foreign origin are present in the decoding transformer supplycircuit.

Considering first the energizing facilities for the relay BPI5, theseare controlled by a contact I02 cf the-code following track relay TR,which in its front or picked up position, completes forthe capacitor II5a charging circuit and which in its back or released positiondisconnects the capacitor from its charging source and connects itacross the'terminalsof the relay winding. The mentioned charging circuitmay be traced from the positive terminal of a suitable supply sourcethrough front contact I02, conductor IIO, the capacitor H5, andconductor II9, back to the negative terminal of the supply source. Thereferred to discharging or relay energizing circuit may be traced fromthe left .or positive terminal of the capacitor II5 through conductorII8, back contact I02 of relay TR, conductor I2I, the winding of relayBPI5, and conductor I22 back to the negative terminal of the capacitor II5.

In operation of the circuits just described, as long as the contacts ofrelay TR. are at rest the winding of relay BPI5 remains deenergized andthe contacts of the relay then, of course, are released. In the event,however, of code following response on the part of the relay TR, thecapacitor II5 becomes charged each time that the relay contacts arepicked up and then is discharged through the winding of BPI5 each timethat the code following contacts are released, By providing relay BPI5with a release retardation sufficient to bridge the intervals betweenpulses F picked up as long as a trackway code is being received.

Accordingly, the device operates in the same manner as the correspondingrelay BP of Fig. 3 and in cooperation with relay H15 it controls, in themanner already explained, the lamps of the wayside signal S at locationQ and aids in selecting the coding of the energy which is supplied tothe rails of the track section to the rear 'of that location.

- In situations where it is desired to control highway crossing signals(not shown), a second repeater relay FPI5 may be added to the apparatusof Fig. 6 by bridging the winding thereof across the terminals of thecapacitor H5 in the manner represented. Should, now, the track relay TRat location Q receive steady energy and continuously hold its contactspicked up, the winding of relay FPI5 will receive operating current overa circuit which may be traced from the positive supply terminal, throughfront contact H12 of relay TR, conductor H8, the winding of relay FPi5,and conductors I24 and H9 back to the negative supply terminal. Underthis condition, contact 86 of the relay becomes effective to completethe energizing circuit for a conventional crossing signal control relayXR (not shown) and thereby discontinue operation on the part of thereferred to highway crossing signals (not shown).

Regarding the advantages of the arrangement of Fig. 6, detection of codeis effected through the use of but a single relay BPI5; the function ofdistinguishing between different code frequencies is performed by asecond relay H15 and conventional circuits; and immunity to falseresponse to rectifier ripples in the supply circuit for decodingtransformer DT8 is obtained by including contact 3'! in the energizingcircuit of relay H15.

From the foregoing description of Figs. 1 to 6, inclusive, it will beseen that all of the herein disclosed embodiments of our invention areeffective to lower the cost, simplify the construction and improve theoperating characteristics of decoding equipment which is suitable forcontrol by a code following relay in railway signalling systems of thecontinuously coded track circuit class. In applying our inventiveimprovements, moreover, none of the desirable features of thisadvantageous form of signalling system control is dispensed with and inall of the represented applications only two sets of contacts arerequired on the code following relay to effect the desired codedetecting and code distinguishing functions.

Although we have herein shown and described only a few forms of railwaytrafiic controlling apparatus embodying our invention, it is understoodthat various changes and modifications may be made therein within thescope of the appended claims without departing from the spirit and scopeof our invention.

Having thus described our invention, what we claim is:

1. In a railway signalling system, the combination of a code followingrelay, a decoding transformer energized over a direct current circuitwhich is pole changed by a contact of said relay, a decoding relay, acircuit connecting the secondary of said transformer in energy supplyingrelation with the winding of said decoding relay, means included in saidcircuit for rectifying the transformer output current which istransmitted to said decoding relay winding, a code detecting relayresponsive to code following operation on the part of said codefollowing relay, and means controlled by said code detecting relay forinterrupting said decoding relay supply circuit whenever said codefollowing operation is discontinued.

2. In a railway signalling system, the combination of a code followingrelay, a decoding transformer energized over a circuit which iscontrolled by said relay, a first repeater relay energized over acircuit which includes a front contact of said code following relay, asecond repeater relay energized over a circuit which includes a backcontact of the code following relay and a front contact of said firstrepeater relay, a decoding relay energized by a rectified portion of theoutput of said decoding transformer, and a front contact of said secondrepeater relay included in the energizing circuit of said decoding relayto interrupt same whenever said code following relay fails to operate.

3. In combination, a code following relay, a. decoding transformerenergized over a direct current circuit which is pole changed by acontact of said relay, a decoding relay, a circuit connecting thewinding of said decoding relay to the secondary of said transformer, arectifier included in said circuit, and a code detecting relayresponsive to code following operation on the part of said codefollowing relay and having a front contact also included in said supplycircuit of the decoding relay for the purpose of interrupting samewhenever said code following operation is discontinued.

4. In a railway signalling system, the combination of a forward and arear section of track, a code following relay operated by energyreceived from the rails of said forward section, a first repeater relayenergized over a circuit which includes a front contact of saidcodefollowing relay, a second repeater relay having slow releasecharacteristics and energized over a circuit which includes a backcontact of the code following relay and a front contact of said firstrepeater relay, means for supplying the rails of said rear track sectionwith coded energy, a contact carried by said second repeater relay forselecting the rate of coding for said energy, and a contact of saidfirst repeater relay included in said rail supply circuit and effectiveupon a release of said first repeater relay for interrupting the supplyto the rear section of energy of the coding rate which the picked-upcondition of said rate selecting contact determines.

5. In combination, a code following relay operated by energy receivedfrom the trackway, a first repeater relay energized over a front contactof said code following relay, a second repeater relay energized over aback contact of the code following relay and a front contact of saidfirst repeater relay, a decoding transformer having portions of an inputwinding which are respectively included in the energizing circuits ofsaid repeater relays, a code distinguishing relay energized from saidtransformer over an untuned circuit which includes other contacts ofsaid code following relay and which transmits energy of sufficientintensity to pick up the relay only when the code frequency of saidtrackway energy exceeds a given rate, and traffic governing meansjointly controlled by said code distinguishing relay and said secondrepeater relay.

6. In a railway signalling system, the combination with a forward and arear section of track of a code following relay operated by coded energyreceived from said forward section, a first repeater relay energizedover a front contact of said code following relay, a second repeaterrelay energized over a back contact of the code following relay and afront contact of said first repeater relay, a decoding transformer alsocontrolled by said code following relay, a code distinguishing relayenergized from said transformer and arranged to pick up only when thecode frequency of said forward section trackway energy exceeds a givenrate, means for supplying said rear section of track with energy of oneor another of a plurality of different codes, circuit means includingcontacts of said second repeater relay and of said code distinguishingrelay for selecting the code for said rear section, and a contact ofsaid first repeater relay included in said circuit means to quicken theshunting response of the apparatus above defined.

'7. In combination with a forward and a rear section of railway track,means for supplying said forward track section with coded energy pulsesthat recur at one or another of three different rates, a code followingrelay operated by energy received from .said forward section, a pair ofrepeater relays and a decoding transformer controlled by said codefollowing relay, a first code distinguishing relay energized from saiddecoding transformer and arranged to respond only to code speeds whichexceed the lowest of said three different rates, a second codedistinguishing relay also energized from said transformer but arrangedto respond only to the highest of said three different code rates, atraflicgoverning signal controlled by said two code distinguishingrelays and a second of said repeater relays, means for supplying saidrear section of track with energy of one or anotherof a plurality ofdifferent codes, and circuit means including contacts of. saidtworepeater relays and of said first code distinguishing relay forselecting the code supplied to said rear section.

8. In a railway signalling system, the combination of a code followingrelay, a decoding transformer controlled thereby, a code distinguishingrelay energized from said transformer and arranged to respond to coderates which are in excess of a predetermined value, a code detectingrelay, acapacitor which receives charging current each time that saidcode following relay picks up, a circuit for discharging said capacitorthrough the winding of said code detecting relay each time that the codefollowing relay releases,

and traffic governing means jointly controlled by said code detectingand code distinguishing relays.

FRANK I-I. NICHOLSON. LESLIE R. ALLISON.

